Cholsesterol is essential for life, around 80% of cholesterol is produced in the liver and each living cell in the body is able to synthesise cholesterol using a complex 37-step process. The first 18 steps are known as the mevalonate or HMG-CoA reductase pathway followed by 19 additional steps. A human adult male weighing around 68kg will normally synthesise about 1 gram of cholesterol per day.
Most cholesterol from dietary sources is poorly absorbed in the gut, when cholesterol is absorbed the body responds by reducing cholesterol synthesis after approximately 7 hours. Cholesterol synthethesis is regulated by he endoplasmic reticulum (responsible for the transport of lipids and proteins) and the mitochondria (the energy plant of all cells).
Cholesterol is used to make products essential for cell survival such as testosterone and vitamin D. High levels of cholesterol and cholesterol precursors have been found in populations with population with low testosterone and low vitamin D.
Low zinc levels are also related to low testosterone and low vitamin D levels, research has shown a direct correlation between zinc levels and cholesterol levels . Pharmacological doses of between 35 mg and 50 mg of elemental zinc have been shown to be effective in lowering cholesterol but lower doses of 15 mg (the RDA for zinc) have no noticeable effect .
Zinc is a major component of membrane-bound transcription factor peptidase site 2. This metalloprotease is essential for the metabolism of cholesterol within the cell. Supplementation with zinc is likely to increase cholesterol conversion to vitamin D and testosterone via this transcription factor.
High levels of cholesterol also increase the activity of matrix metalloproteases that result in the degradation of the collagen fibres within the extracellular matrix resulting in thinner hair that sheds prematurely.
A study conducted on 827 Italian factory workers in 1990 showed that men with no hair loss had an average cholesterol level of 5.369 mmol/L, men with receding hairlines had an average cholesterol level of 5.387 mol/L and men with more sever hair loss had an average cholesterol level of 5.521 mol/L.
The central finding of one study , was that excess cholesterol within the hair follicle niche can trigger an innate immune response that leads to the induction of Toll-like receptor and Interferon gamma gene expression.
This leads to the activation and recruitment of T cells and macrophages that surround the hair follicles and initiate an inflammatory response resulting in the hair less lesions seen in alopecia areata.
Hair loss associated with abnormal cholesterol metabolism is also seen in women with low, normal or high levels of cholesterol. It appears the ratio of high density lipoproteins compared to low density lipoproteins is the factor that affects hair growth.
Cholesterol is required for the synthesis of testosterone and vitamin D. Abnormal levels of cholesterol are associated with hair loss in men and women.